1. Field of the Invention
The present invention relates to a brake device for a vehicle. In particular, the present invention relates to a brake device for a motorcycle.
2. Description of Background Art
A hydraulic brake device which is popularly used in a vehicle such as a motorcycle includes a braking input side which allows a driver to generate a liquid pressure by manipulating a brake manipulation portion and a braking output side which supplies the liquid pressure to a wheel control mechanism. The braking input side and the braking output side communicate with each other or are interrupted from communication with each other by way of an electromagnetic valve.
As an example, there has been known a so-called bi-wire-type brake device in which a manipulation variable of the brake manipulation portion is electrically detected. A liquid pressure generating device is controlled in response to a detection value thus generating a liquid pressure. In addition, a vehicle control mechanism is manipulated (see JP-A-2001-310717, for example).
In such a bi-wire-type brake device, for example, a master cylinder which is interlockingly operated with a brake lever (brake manipulation portion), and a brake caliper (wheel braking mechanism) which imparts a braking force to the wheel by a hydraulic manipulation are connected with each other by a brake passage which is provided with a normally-open electromagnetic open/close valve. A hydraulic modulator, which supplies the liquid pressure generated by an electrically-operated actuator to the brake caliper, is connected to a brake caliper side of the brake passage from the above-mentioned electromagnetic open/close valve.
In such a brake device, at the time of performing the braking operation, the brake caliper and the hydraulic modulator are separated from the master cylinder by closing the above-mentioned electromagnetic open/close valve thus controlling the electrically-operated actuator in response to the liquid pressure of the braking input side so as to allow the hydraulic modulator to generate a liquid pressure of the braking output side. Therefore, the generated liquid pressure is supplied to the brake caliper thus performing the braking operation. In this case, to enhance the responsiveness or to stabilize the braking performance, it may be possible to close the brake passage by closing the above-mentioned electromagnetic open/close valve when an ignition switch is turned ON or a vehicle speed reaches a given vehicle speed thus ensuring a standby state from a non-braking time.
In this manner, in the brake device which controls the electrically-operated actuator in response to the liquid pressure of the braking input side so as to control the liquid pressure of the braking output side (that is, the supply pressure to the brake caliper), a pressure sensor for detecting the liquid pressure of the braking input side and a pressure sensor for detecting the liquid pressure of the braking output side become necessary. Therefore, conventionally, one pressure sensor is respectively provided to the braking input side and the braking output side.
However, with respect to the conventional brake device, which is provided with one pressure sensor at the braking input side and one pressure sensor at the braking output side, there exists a following difficulty in performing a trouble diagnosis or troubleshooting the pressure sensor at the braking input side.
With respect to the pressure sensor at the braking output side, the trouble diagnosis can be performed by comparing an output value of the pressure sensor at the braking output side and an operation state of the electrically-operated actuator (for example, a current value of a drive motor, a detection value of a crank angle sensor or the like).
On the other hand, with respect to the pressure sensor at the braking input side, in a state that the braking input side and the braking output side are in communication with each other, it is possible to perform the trouble diagnosis by comparing the output value of the pressure sensor at the braking input side and the output value of the pressure sensor at the braking output side. However, in a state that the braking input side and the braking output side are interrupted from each other, there exists no comparison object and hence, the trouble diagnosis of the pressure sensor at the braking input side using the above-mentioned method is difficult.